Polarization-division multiplexed solitons in optical fibers with polarization-mode dispersion

We point out that the use of polarization-division multiplexed solitons is only preferable to a copolarized pulse train only if the system is interaction-limited and the polarization-mode dispersion (PMD) is sufficiently weak. If the PMD is stronger, copolarized solitons perform better than polarization-division multiplexed ones. A simple analytical formula for when this occurs is derived.